Telephone-repeater.



A. H. ULSSON & H. B. M. PLEIJEL,

TELEPHONE REPEATEH.

APPLECATION FILED NOV. 28. 1914.

1 ,1 89,728. Patented July 4, 191(3.

. G A A H D D H Q/Vi finesse/o /.7. h. M

61 Howie z Suva You.

, UNITED sTATEs PATENT oEFIoE.

AXEL HERMAN OLSSON AND HENNING BERNHARD MATHIAS PLEIJEL, F STOCKHOLlE,

SWEDEN.

TEnEPHoNE-EEPEATER.

Specification of Letters Patent.

, Patented July 4, 1916.

Application filed November 28, 1914. Serial No. 874,533.

son', engineer, and HENNING BERNHARD NIATHIAS PLEIJEL, professor, both subjects;

of the King of Sweden, citizens of Sweden,

and respectively residing at Bergsgatan 16 and Brunnsgatan 2, Stockholm, in the Kingdom of Sweden, have invented certain new and useful Improvements in Telephone-Repeaters, of which the following is a specification.

As is well known, so-called telephone repeaters have been used in telephone apparatus for the purpose of separating two lines, so that direct current, or a current comparable thereto, does not pass over from the one line to the other. For instance, telephone repeaters are used for connecting single lines with double lines. All such telephone repeaters as hitherto constructed consist of two windings, which are wound upon a common iron core common to both. In recent times extensive use has been made of such telephone repeaters. They have, for instance, been employed to connect lines of different kinds (cable line and free line) for the purposes of removing to the greatest possible degree the reflection of telephone waves, which would otherwise arise." Further, such telephone repeaters have been entensively used in combination lines for telephony and telegraphy. In proportion as the length of telephone lines has been increased, it has become necessary to improve these telephone repeaters in every respect, so that they may repeat with the slightest possible loss the high frequency speech currents as well as the currents with lower period numbers, which are used for calling.

Two telephone repeaters of the Western Electric type, when inserted in a line, offer a resistance to the arriving speech currents .equal to that of three miles of the British Standard? cable, and these telephone repeaters are considered the best now available. The telephone repeaters of the British post olfice offer, on the contrary, to the arriving speech currents a resistance equal to that of 10 to 12 miles of the British Standard cable. With regard to the transmission of calling currents, however, the conditions are reversed, that is to say, the telephone repeater of the British post oflice is superior to that of the Western Electric type, and as hereinafter further stated, this results from the principle of their construction (two windings upon the same iron core), which alwaysentails the consequence that a reduction of the speech current loss affects the calling currents and vice versa.

In an article published in Oompte Rendue de la [1 Conference Internationale des Technicz'ens ales Tele'gmpkes et ales Telephones die ZEurope, Paris 1910 with the title \Sw' Ze caZcuZ des enroulments un tramformateur telephonz'que, are explained the conditions under which the best effect of a telephone repeater is obtained. From when currents are being dealt with whereof the respective number of periods lie between certain limits. Practical tests made with correspondingly constructed telephone repeaters have fully verified the said theory.

An ideal repeater for telephonic purposes should have such characteristics that it has an improving action upon the speech currents as well as upon the calling currents used in telephone traffic. As above stated, it is impossible to obtain this effect by pursuing the principle hitherto followed; namely, two windings on a core common to both. To solve the problem, we employ a combination of two telephone repeaters, one of which isconstructed so as to act in the best possible way for the speech currents, while the other is calculated to act in the best way for the calling currents. It is not suflicient however, to. merely connect these two coil devices together, seeing that, if they be coupled in series, the combination would act as a repeater, acting very inefficiently both for the speech currents and for the calling currents. The same condition would, of course, exist if the coils were coupled in parallel. The I coils must be so arranged that the action of the one coil will not be affected by the other coil, and in order to obtain this object, we utilize the property inherent to a condenser of acting in different ways upon high frequency and low frequency currents. As is well known, the impedance of a condenser is reduced in proportion as the number of periods increases. A condenser, therefore, which acts as a high resistance for the low frequency calling currents, transmits the I speech currents without difliculty.

In the accompanying drawings, Figure 1 is a diagrammatic view illustrating a system arranged accordin to our invention; Fig. 2 being a similar-view illustrating a modification thereof.

To attain a complete balance, the two windings of the speech current coil are each subdivided into two halves arranged one on each side of thecalling current coil E or E The primary winding of the speech current coil thus consists in the system shown in Fig. 1, of A, B and C, D; the secondary winding of A B and C D Between B and C and between B and O is inserted a condenser F or F of corresponding capacity.

To adapt the system for use in duplex lines, the middle point of the secondary winding E of the calling current coil is taken out. The speech currents now select, on account of their high number of periods, the path A, B, F, C .D, in the primary circuit and the path A 13 F (1 ,1) in the secondary circuit. The speech current coil may, accordingly, be I constructed exclusively for currents of a" number of periods, which lie between the limits for the speech currents. According to the theory, this coil will then be constructed with a comparatively small number of windings and with a core of finely-dividediron. The coil may if desired, be specially calculated for the line in order to obtain the best possible result. In the case of the calling currents, on the contrary, the condensers act as high resistances, whereupon these currents select the paths A. B, E, C, D, and A B F, C D In order to obtain a good transmission of the calling currents, the

calling current coil may thus be constructed so as to act. upon the transmission in the most favorable manner. According to the theory, this coil should be Wound with a with the condensers in the manner shown in Fig. 2.

'A, B, and C, D are the primary windings, A B and C, D the secondary windings of the speech current coil.

G, H is the primary winding and G H the secondary winding of the calling current coil.

F and F are the two condensers.

- In view of the great impedance of the windings G, H and G H? for the speech currents, these latter here select the paths A, B, F, C, D, and A B F C D The calling currents, on the contrary, to which the condensers offer a high resistance pass through G, H, or G H.

We claim 1. A telephone repeater for speechas well as for calling-currents,- embracing two induction-coils whereof one is adapted for working with the speech-current and, the other for working with calling-currents.

2. A telephone repeater comprising two induction-coils wherein thejprimary windings and the secondary windings are respectively connected up in series, and whereg in the calllng-current source is bridged by a capacity.

In testlmony whereof we have afiixed our signatures in presence of two witnesses;

AXEL HERMAN OLSSON. HENNING BERNHARD MATHIAS PLEIJEL.

\Vitnesses SALLY J'UKE, GRETA PRIEN.

The iron core is thus con can also be obtained by combining them 

